43991609 has 4 divisors (see below), whose sum is σ = 44418816. Its totient is φ = 43564404.

The previous prime is 43991599. The next prime is 43991653. The reversal of 43991609 is 90619934.

43991609 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 90619934 = 2 ⋅45309967.

It is a cyclic number.

It is not a de Polignac number, because 43991609 - 2¹² = 43987513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (43991209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 213449 + ... + 213654.

It is an arithmetic number, because the mean of its divisors is an integer number (11104704).

Almost surely, 2^43991609 is an apocalyptic number.

It is an amenable number.

43991609 is a deficient number, since it is larger than the sum of its proper divisors (427207).

43991609 is a wasteful number, since it uses less digits than its factorization.

43991609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 427206.

The product of its (nonzero) digits is 52488, while the sum is 41.

The square root of 43991609 is about 6632.6170551299. The cubic root of 43991609 is about 353.0123903234.

The spelling of 43991609 in words is "forty-three million, nine hundred ninety-one thousand, six hundred nine".